[Bug rtl-optimization/48702] New: optimization regression with gcc-4.6 on x86_64-unknown-linux-gnu

[mariah.lenox at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48702

           Summary: optimization regression with gcc-4.6 on
                    x86_64-unknown-linux-gnu
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
        AssignedTo: unassig...@gcc.gnu.org
        ReportedBy: mariah.le...@gmail.com


/* optimization regression with gcc-4.6.0 on x86_64-unknown-linux-gnu

% gcc-4.6.0 -O2 -o foo foo.c
% foo
% 1
%
% gcc-4.6.0 -O1 -o foo foo.c
% foo
% 4
%
% gcc-4.5.1 -O2 -o foo foo.c
% foo
% 4

% gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/local/gcc-4.6.0/x86_64-Linux-core2-fc/libexec/gcc/x86_64-unknown-linux-gnu/4.6.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: /usr/local/gcc-4.6.0/src/gcc-4.6.0/configure
--enable-languages=c,c++,fortran --with-gnu-as
--with-gnu-as=/usr/local/binutils-2.21/x86_64-Linux-core2-fc-gcc-4.5.1-rh/bin/as
--with-gnu-ld
--with-ld=/usr/local/binutils-2.21/x86_64-Linux-core2-fc-gcc-4.5.1-rh/bin/ld
--with-gmp=/usr/local/mpir-2.3.0/x86_64-Linux-core2-fc-gcc-4.5.1-rh
--with-mpfr=/usr/local/mpfr-3.0.0/x86_64-Linux-core2-fc-mpir-2.3.0-gcc-4.5.1-rh
--with-mpc=/usr/local/mpc-0.9/x86_64-Linux-core2-fc-mpir-2.3.0-mpfr-3.0.0-gcc-4.5.1-rh
--prefix=/usr/local/gcc-4.6.0/x86_64-Linux-core2-fc
Thread model: posix
gcc version 4.6.0 (GCC) 
%

*/

#include  <stdio.h>

#define LEN 4  

void unpack(int  array[LEN])
{
int ii, val;

val = 1;
for (ii = 0; ii < LEN; ii++) {
  array[ii] = val % 2;
  val = val / 2;
}

return;
}

int  pack(int  array[LEN])
{
int ans, ii;

ans = 0;
for (ii = LEN-1; ii >= 0; ii--) {
  ans = 2 * ans + array[ii];
}

return ans;
}

int  foo()
{
int temp, ans;
int array[LEN];

unpack(array);
temp = array[0];
array[0] = array[2];
array[2] = temp;
ans = pack(array);
return ans;
}

int main(void)
{
int val;

val = foo();
printf("%d\n", val);

return 0; 
}